Continuous casting molds of the same general type as that of this invention, have been known for many years, see e.g., German Pat. No. DE-PS 887,990. They are formed with generally parallel side walls, which are provided with internal cooling and which define a mold cavity having a cross section in the shape of an elongated parallelepiped corresponding to the approximate size and shape of the strip being cast. The upper area of the mold into which the molten metal is poured through the pouring tube is generally funnel-shaped or flared sufficiently to provide room for the tube (plus a necessary "safety" clearance), with the walls tapering down below the tube to the configuration of the strip being cast. During pouring and while the continuous casting is in progress, the level of the molten metal is maintained substantially above the exit ports of the pouring tube, and due to the cooling, the metal commences to congeal while still in the flared area, where it initially develops a thin and relatively fragile strand casting shell in the upper area of the mold. The amount of flare in the upper area of the mold is determined by the diameter of the pouring tube, the desired immersion depth of the pouring tube, and the required clearance between the pouring tube and the side walls of the mold.
One problem with such molds in use is that the nascent, and hence fragile, strand shell in the upper area of the mold tends to form wrinkles due to the decrease in surface area of the mold as it tapers down to the final size and shape of the casting. Such wrinkles should be avoided because they introduce problems during the further processing of the product by rolling, which problems become more serious the thinner the cast strip is. Also such wrinkles tend to increase the risk of local bleeding from the liquid core of the casting toward the surface. The tendency to form wrinkles, however, also increases as the angle of the flared area of the mold increases. The result is effectively to limit the thickness of the strip being cast because the pouring tube cannot be smaller than a given minimum diameter, and if the upper part of the flared area is fixed, the lower part cannot be decreased in thickness without increasing the flare angle which, in turn increases the risk of forming wrinkles.